Many rivers are interrupted in their continual flow of material and water (River Continuum Concept, VAN-NOTE et al. 1980) by weirs and hydroelectric power plants. Along the River Ilm (Thuringia, Germany), with a length of 130 river kilometres, 57 weirs were built. These transverse structures influence not only the continuous transport of suspended and dissolved materials but also several other environmental factors, such as velocity and sedimentation rate. The highest microbial activity takes place in the biofilm (surface-associated organisms) in small streams or in the rhithral region of streams (SCHWO-ERBEL 1994). Knowledge of the role of substrate-associated protozoans is modest. Heterotrophic flagellates are the major consumers of bacteria and transform dissolved organic matter into particulate organic matter, which in turn is available for consumers in the classic food chain (AZAM et al. 1983). The present study investigated the influence of weirs on the colonization of biofilms, especially on the associated heterotrophic flagellate communities.
展开▼
